Dang leaking primer 3116

peterkvs

peterkvs

Active Member
Nov 11, 2012
511
Guntersville, Alabama
Boat Info
400 Sundancer 1999
Engines
3116 Cats, 1000 hours
The primer on my Cat 3116 has been dripping for a year now. It's a slow drip and doesn't seem to always drip. It drips right out from under the knob of the pump handle. I finally got fed up with the mess and paid Cat $220 for a new quarter turn valve, which I assumed was what isolated the primer from the fuel system. Anyway, i installed the new quarter turn valve and the sob is still dripping. I suppose the next thing to replace is the primer pump assembly. I wish now I had bought the 1/4 turn valve with the primer pump rather than separately. May have saved some time and money. And I did check the operation of the 1/4 turn valve prior to installation and it seemed correct.

Thoughts?

Pete
 
If the ball valve is new and it is closed, then fuel cannot flow. Either the index on the valve is slightly off and you are leaving it open a little bit, or the priming pump had leaked fuel in it and it is just finding its way up the stem and out. I'd give it an hour or 2's running time and see what happens.

You may remember me posting that I don't use the priming pumps for this exact reason........the suckers leak. I finally found the closed position in the ball valves and they've been closed for 15 years now. (Yeah, I know what Caterpillar says about using the priming pump.......but Cat isn't here to clean up the mess!)
 
Frank,

Based on your previous advice on the index of the ball valve I carefully checked it before installing it and it was perfectly indexed. However, you might be exactly right that the primer had fuel in it and it is vibrating out past the shaft. I can just take the primer off of the 1/4 turn valve and assure that it is not leaking. Also drain it out completely. The primers on these engines are just garbage. I was going to pre-fill the filters when I changed them along with the 1/4 turn valve replacement, but the diesel pump at the marina was broken so I had to do it the primer method. I think there is a port on the fuel filter housing that you can remove and use a vacuum pump to suck fuel into the filter. Do you know anything about that?

Thanks as always.

Pete
 
I had a drip on one and replaced it ($165) and then the other started with the occasional lil drip and it has a paper towel folded and wrapped around it with a twist tie holding it in place.... I have not mopped up a drip in 4 years...
 
Pete,

I think there is, but Cat "isn't forthcoming" because they want all the filter in the secondary to be filtered fuel. If they advise opening a filter port, there is some idiot somewhere that is going to try to pour fuel in it.

I have a 2.5gal plastic container that I only use for filter changes and I never buy that fuel at the marina because I know how often them pump mounted filter isn't changed. I just go by the local truck stop and get clean fuel from a source I know to be frequently cycled and serviced.
 
If you have the MA500 Racor's the only place you could possibly apply suction and fill them with fuel is at the Tee handle. Assume the filter element is installed and the Tee handle was bored and tapped for something like a vacuum gauge. The tube under the lid that the handle threads into is also the fuel passage to the engine (that is why it's where vacuum is measured to determine filter performance). If you pulled a vacuum through the Tee handle you would be pulling fuel from the tank and through the Racor filter element. There is no other place on the filter assembly that this can be done and also fill the filter housing. Defender sells a bored and tapped Tee handle if one should want to go down that road. There are a series of check valves in the injector pump so vacuum on the filter housing will definitely pull fuel from the tank.

My opinion is that filling the housing full with clean fuel from a container is just fine. Remember the Cat filter (10 or 5 micron) on the engine is still there and it will capture anything that may get through to it. I change the engine filter every year so it's highly unlikely it will plug up filling the Racor a couple times a year.

Also, on that primer pump, if you remember, the plunger on mine would unlock and extend every time I ran the boat for any length of time at all. As it ended up that little ball valve was the issue and was leaking and pressurizing the pump (thanks Mr. Webster for the insight on that); it also leaked badly through the stem. I disassembled the unit and found the clocking of the ball relative to the handle was off and it was never fully closing. I fixed that and leak is gone unless I open it and cycle the pump.
 
Last edited:
I took his question to mean the Cat secondary filter housing because sucking the fuel out of the top of the housing would also fill the secondary filter which is the function of the priming pump.
 
Guys,

There is a plug on the side of the secondary filter that the CAT tech pointed to and said that is what they use to prime the system. I imagine screwing in a barbed fitting and connecting to my suction oil change pump and sucking fuel from the tank, through the racor and through the cat secondary filter. I have not tried it, and was just wondering if anyone has.

I replaced my leaking 1/4 turn valve on the primer and it was still dripping. I removed the primer from the valve and noted that it was not leaking from the new 1/4 turn valve and that the fluid left in the primer after pumping was just vibrating out and making the mess. I cleaned out the pump completely and now there is no more mess. Until next time anyway.

Pete
 
It might be easier to just fill the secondary from a clean jug of fuel, like you do the Racors, than to spend the time and effort to rig up some sort of a pump. Additionally, Parker Filtration, the parent company of Racor has an add-on priming pump you might consider, but I suspect it is expensive and that you might not have space under your filter on the 400/410. It is so easy to hand fill the filters that I never looked into it.
 
Sorry, I was confused in my last post... Now my Cat mechanic said that he doesn't worry about priming anything; he sets the throttle full and cranks the engine. I watched him do this and after several tries the engine coughed to life, none the worse... I was amazed how fast the Racor filled; the injector pump moves a lot of fuel....
 
I'm not in a position to disagree with your mechanic, but I'll just ask you if you have ever had the fun(?) of purging air out of a 3116/3126? Just cancel your afternoon plans!
 
Yeah, you don't want to run the engines with an empty filter, either filter. I made that mistake once.
 
Here is what I can tell you- the mechanic was finishing replacing the fuel system check valves, replacing fuel pumps, setting the rails, and replaced the Cat fuel filter and I stopped by to see how things were going. He was just finishing up and was setting up to run the engines; I offered to prime the fuel system but he said no problem it will start... Well four or five start attempts and it ran, albeit it sounded like a sick GM Diesel Cadillac but as RPMs came up he pulled the throttles back and all was good. I'm a believer....
 
I have a feeling CAT put a priming pump on for a reason.
 
Ok, the primer pump is still pissing me off because after spending $280 on a new quarter turn valve the damn thing still leaks. Tonight I took off the primer pump and ran the engine. At idle nothing came past the quarter turn valve or the check valve, but at higher rpm a small amount weeps past. I installed a new primer pump that has good seals which will probably solve the problem, but I really wonder if the new quarter turn valve is defective. It's under waranetee for another month. Now I wish I hadn't thrown away the original one.

Tomorrow I leave for a 200 mile trip. I hope it doesn't leak the whole way there and back.

Thoughts?

Thanks. Pete
 
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